1. Field
The disclosure relates to a control circuit for a synchronous rectifier-type DC-DC converter, a synchronous rectifier-type DC-DC converter and a control method thereof.
2. Description of Related Art
Portable electronic devices such as notebook computers generally employ DC-DC converters. In the portable electronic devices, power consumption of the DC-DC converters needs to be reduced to thus make the devices operational for a longer period of time.
Japanese Patent Publication No. H8(1996)-289535 discloses a DC-DC converter comprising an output value monitoring section that monitors an output voltage to determine whether a power supply is required with respect to a load, a current monitoring section that monitors a current flowing to a coil connected to an output terminal to determine whether a power supply is required with respect to a load, and a control section that places a switching section connected to the coil in an ON state or an OFF state, based on monitoring results of the output value monitoring section and monitoring results of the current monitoring section.
In the above-described DC-DC converter, if a power supply is required with respect to a load, the control section places the switching section in an ON state to supply power to the load, based on monitoring results of the output value monitoring section. At this time, the control section shifts to a mode in which an output is not received from the output value monitoring section.
When the switching section enters an ON state in the above-described DC-DC converter, the current flowing to the coil is increased. When the current monitoring section confirms that the coil current has reached a first current value, the control section places the switching section in an OFF state to thereby stop the supply of power to the load. When the switching section enters an OFF state, the current flowing to the coil is decreased. When the current flowing to the coil reaches a second current value, the control section returns to a mode in which an output is received from the output value monitoring section, to thereby monitor whether a power supply is required with respect to the load. The control section controls the switching section to an ON state or an OFF state, and as a result, the above-described DC-DC converter executes a series of power supply operations.
In the above-described DC-DC converter, the first and the second current values can be changed. Here, the first and the second current values are set accordingly in the above-described DC-DC converter, thereby allowing to set a cycle of power supply operations to a desired value and supply the required power to the load, while reducing the number of switchings. Accordingly, in the above-described DC-DC converter, by reducing the number of switchings, it is possible to suppress power losses, thereby reducing power consumption.